Solid ink or phase change ink printers encompass various imaging devices, such as printers and multi-function platforms. Solid ink printers offer many advantages over other types of image generating devices, such as laser and aqueous inkjet approaches. These advantages include higher document throughput, sharp colors, and less packaging waste for the ink consumed by the printer.
A typical solid ink imaging device includes an ink loader, which receives solid ink units, such as ink sticks or pellets. These ink units remain solid at room temperatures so a user can conveniently store solid ink in proximity to a device and handle the solid ink during the loading phase without mess or staining. Coupled to the ink loader is a feed channel through which multiple units of the solid ink may be transported for delivery to a melting assembly. Thus, the ink is loaded by a user in solid form into the ink loader and then the solid ink is moved into the feed channel for delivery to the melting assembly. In most color solid ink imaging devices, an ink loader includes a plurality of feed channels, one for each color of ink used in the device. These multiple feed channels and melting assemblies are typically provided in parallel in the imaging device.
For example, FIG. 1 shows a previously known solid ink, or phase change, ink printer 10 that includes an outer housing having a top surface 12 and side surfaces 14. A user interface display, such as a front panel display screen 16, displays information concerning the status of the printer, and user instructions. Buttons 18 or other control elements for controlling operation of the printer are adjacent the user interface window, or may be at other locations on the printer. An ink jet printing mechanism (not shown) is contained inside the housing. An ink feed system delivers ink to the printing mechanism. The ink feed system is contained under the top surface of the printer housing. The top surface of the housing includes a hinged ink access cover 20 that opens as shown in FIG. 2 and FIG. 3, to provide the user access to the ink feed system.
In the particular printer shown, the ink access cover 20 is attached to an ink load linkage element 22 so that when the printer ink access cover 20 is raised, the ink load linkage 22 slides and pivots to an ink load position. As seen in FIG. 2, opening the ink access cover reveals a key plate 26 having keyed openings 24A-D. Each keyed opening 24A, 24B, 24C, 24D provides access to an insertion end of one of several individual feed channels 28A, 28B, 28C, 28D of the solid ink feed system (see FIG. 2).
Each longitudinal feed channel 28A-D delivers ink sticks 30 of one particular color to a corresponding melt plate 32. Each feed channel has a longitudinal feed direction from the insertion end of the feed channel to the melt end of the feed channel. A melt plate 32 is located at the melt end of the feed channel. The solid ink stick is changed into a liquid form by the melt plate 32 and the melted ink is provided through gap 33 to a liquid ink reservoir (not shown). The feed channels 28A-D have a longitudinal dimension from the insertion end to the melt end, and a lateral dimension, substantially perpendicular to the longitudinal dimension. Each feed channel in the particular embodiment illustrated includes a push block 34 driven by a driving force or element, such as a constant force spring 36, to push the individual ink sticks along the length of the longitudinal feed channel toward the melt plates 32 that are at the melt end of each feed channel. The tension of the constant force spring 36 drives the push block toward the melt end of the feed channel. The ink load linkage 22 is coupled to a yoke 38, which is attached to the constant force spring 36 mounted in the push block 34. The attachment to the ink load linkage 22 pulls the push block 34 toward the insertion end of the feed channel when the ink access cover is raised to reveal the key plate 26.
A color printer typically uses four colors of ink (yellow, cyan, magenta, and black). In the four color ink printer shown in FIG. 2, each feed channel receives ink sticks 30 of a single color. The operator of the printer exercises care to avoid inserting ink sticks of one color into a feed channel for a different color. The key plate 26 has keyed openings 24A, 24B, 240, 24D to aid the printer user in ensuring that only ink sticks of the proper color are inserted into each feed channel. Each keyed opening 24A, 24B, 240, 24D of the key plate has a unique shape. The ink sticks 30 of the color for that feed channel have a shape corresponding to the shape of the keyed opening. The keyed openings and corresponding ink stick shapes exclude from each ink feed channel ink sticks of all colors except the ink sticks of the proper color for that feed channel.
In another loading system for a solid ink printer, a mechanized drive provides solid ink to a melting assembly. As shown in FIG. 4, a curved feed channel 114 includes an endless belt 118 mounted around pulleys 120 at least some of which are driven by a motor and gear train 122 or the like. An ink stick 126 placed in the port 124 engages the belt 118 and is carried along the feed channel 114 in response to the pulleys 120 being driven. After transitioning through the curve 128, the ink stick begins a fall towards a melting assembly 130.
In order to sense the presence of ink sticks in the vertical section of the feed channel 114, one or more mechanical flags may be provided. As shown in FIG. 4, a low ink flag 136 is positioned near the end of the transition section and an out of ink flag 140 is positioned near the melting assembly. The mechanical flag may be a finger that is biased to move into the ink stick path. An ink stick moving through the feed channel 114, however, urges the flag against the biasing action to displace the flag from its path as it passes a flag. The presence of the flag may be electrically sensed to generate a signal that indicates whether an ink stick is acting on a flag or not. For example, if the low ink flag indicates no ink stick is acting on it to move it out of the ink stick path, then a signal is generated that indicates only a number of ink sticks corresponding to the length of feed channel below the low flag to the melting assembly may be present in the feed channel. Similarly, if no ink stick is acting on the out flag, then an insufficient amount of ink stick is in the vertical portion of the feed channel to provide a reliable supply of solid ink to the melting assembly for use in the printer. In response to the signal generated from the low flag or out flag indicating no ink stick is opposite the flag, a controller in the printer may activate the motive force to the pulleys 120 to transport ink sticks to the vertical section of the feed channel to replenish the stack of ink sticks against the melting assembly.
In some previously known solid ink printers that use biased flags to indicate low solid ink conditions, the controller coupled to the flags would generate a refill signal to an operator in response to one flag transitioning to the low or out condition that indicated the operator should refill all of the feed channels even though only one channel had reached the low or out condition. In other previously known solid ink printers, the controller generates a signal to refill only the channel or channels that are experiencing the low or out condition that caused the flag to transition. While this method of operation helps eliminate attempts to reload a channel that does not require refilling, it does not provide an accurate measurement of the amount of solid ink within a feed channel. Instead, this type of feed channel status system only indicates whether the feed channel is almost out of or is out of solid ink. Consequently, a solid ink stick loader system that provides an indication of the amount of solid ink in each feed channel is desirable.